Method and apparatus for heating solid and liquid particulate material to vaporize or disassociate the material

ABSTRACT

A method and apparatus for heating solid and liquid particulate material to vaporize or dissociate the material uses an arc wall, generated by a revolving arc, to increase residence time of the material until it is at least vaporized. The arc wall passes gas or vapor but is impervious to the passage of solid or liquid particulate material that is incident upon the wall.

0 United States Patent 11 1 1111 3, 7 Kofoid 51 Dec. 9, I975 [54] METHODAND APPARATUS FOR HEATING 3,309,550 3/1967 w61r61a1 219/121 P SOLID ANDLIQUID PARTICULATE 3,344,051 9/1969 Latham 250/546 X 3,347,774 10/1967Myers 250/530 gMTERIAL To VAPORIZE 3,533,756 10/1970 Houseman 117/931 RISASSOCIATE THE MATERIAL 3,592,627 7/1971 Neuenschwander 75/.5 BB [75] It M l i J K f id Seattle, w 3,684,667 8/1972 Sayce 75/10 x 3,720,5983/1973 Thompson 204/164 x [73] Asslgneez The Boeing Company, Seattle,3,733,387 5/1973 Kugler et al. 1. 423/33 C Wash. 3,749,763 7/1973Scammon 61 a]. 423/608 Filed. Jan 30 1973 3,796,591 3/1974 Shoumakerll7/93.l PF

[2]] Appl. No.: 327,914 Primary Examiner-F. C. Edmundson Attorney,Agent, or FirmSeidel, Gonda &

h 52 us. c1. 204/164; 23/194; 75/5 1313; Gold ammer 117/931 PF; 219/122;250/542; 423/336; 423/608 51 1111. c1.= COlG 27/04; c011= 7/30 {57]ABSTRACT [58] Field 61 Search 204/164; 75/.5 BB; A method and apparatusfor heating solid and liquid 23/33 L, 608; 250/542; 219/122, 76, 121 P;particulate material to vaporize or dissociate the mate- 117 93 pp;23/294 rial uses an arc wall, generated by a revolving arc, to

increase residence time of the material until it is at [56] R f Citedleast vaporized. The are wall passes gas or vapor but is UNITED STATESPATENTS impervious to the passage of solid or liquid particulate2,074,530 3/1937 Baumann et al .1 250/542 X material that ls mcldentupon the wan.

3,308,050 3/1967 Denis 250/542 x 27 Claims, 4 Drawing gums U.S. PatentDec. 9, 1975 Sheet 2 of 4 F/GZ I I I r I l I z I I I I I US. Patent Dec.9, 1975 Sheet4 014 3,925,177

METHOD AND APPARATUS FOR HEATING SOLID AND LIQUID PARTICULATE MATERIAL TVAPORIZE 0R DISASSOCIATE THE MATERIAL This invention relates to a methodand apparatus for heating solid and liquid particulate material tovaporize or dissociate the material. More particularly, this inventionrelates to the use of a revolving arc to heat and vaporize liquid orsolid particulate material by increasing residence time of thematerial'in a high temperature zone.

There are many circumstances in which it is desirable to vaporizematerials which reach that condition only at very high temperatures,such as in excess of 2000K. Refractory materials are among those thatdesirably must be heated to vaporization temperatures. An example ofsuch a material is Al,0, which vaporizes at above approximately 3900I(.An exemplary purpose for vaporizing ai is described in co-pending patentapplication Ser. No. 269,634 filed July 7, 1972 for Method and Apparatusfor Reducing Matter to Constituent Elements and Separating One of theElements from the Other Elements. Other uses for the invention should beobvious to those skilled in the art from what is described herein.

There are several known heat sources capable of heating materials ofthis type to varporization. Among these are radio frequency inductiondischarge devices, plasma jet devices, and electric are devices. Radiofrequency discharge devices have certain advantages not present inplasmajet and are devices, such as long residence time in the hightemperature region. However, they are not commercially economical,particularly where large amounts of power are to be used to heatrelatively large amounts of material. Plasma jet heating devices and areheating devices are different forms of high current are devices. Assuch, they both have in common two basic enthalpy transfer problems.First, because a gas is heated as it approaches an arc, the denity ofthe gas (and of the particle carried in it) is reduced. The result isthat most of the mass (gas and solid) tends to avoid the hightemperature zone or the discharge channel as in the case of a plasmajet. indeed, rather little of the mass passes through it. The secondenthalpy problem is one of residence time; that is, the time duringwhich the material to be heated is in the vicinity of the arc. Theresidence time cannot be extremely short if the refractory or othermaterial is to he vaporized, dissociated, or perhaps even ionized. Acorollary to the foregoing is that heat transferred to a solid or liquidis governed by the enthalpy as well as the temperature of thesurrounding gas. For high rates of heat transfer, the solid or liquidmust be enveloped in a dissociated gas.

Electric arcs for heating can be divided into two groups for the purposeof evaluating the differences between arc heating devices. The moststraighforward form of arc heating is to heat a volume of gas only in ahighly thermally insulated chamber. In such a case, the total enthalpyis carried to gas in the chamber, the residense time of the material tobe heated in the gas is long, and the gas is in intimate contact withthe material. For this type of heating, constricted arc discharges inthe form of pisma jets are entirely suitable. Such devices evidence ahigh efficiency and have been used effectively. For example, very highenergy units have been constructed for high temperature wind tunnels.High efficiency can also be obtained for heating a volume of gas only bythe use of long column a.c. polyphase arcs placed in the gas flowentering a chamber. But high efficiency heating using plasma jets ora.c. polyphase arcs is limited to gas only heaters. When attempting toheat liquid or solid material, the problem of mass avoidance and shortresidence time greatly reduces the efficiency of plasma jet and acpolyphase arc heaters.

When using an arc heating device to heat liquid or solid materials to anevaporated, dissociated or even ionized condition, the problem changesfrom that of simply heating the gas to that of transferring sufficiententhalpy to the liquid or solid. High speed gas flow plasma heaters aredisadvantageous because of the short residence time. Materials whichrequire high tem peratures to vaporize can be vaporized only if theypass through a part of the discharge volume where the gas is momentarilydissociated. This is necessary for large enthalpy transfer to the solidor liquid. Thus, as indicated above, plasma jets are not well suited forthis heating task. Their difficulties are short resident time andgetting an appreciable proportion of the liquid or solid material intointimate association with the arc and the dissociated gas.

The present invention seeks to overcome the problems of other types ofheaters by using a revolving arc to keep the solid or liquid material tobe heated in close proximity to the plama for a residence timesufficiently long to effect the necessary transfer of energy. Therevolving arc forces the material to be heated into the hottest plasmavolume, where the gas is dissociated, in order to transfer the heat ofreassociation to the solid or liquid material. in particular, thepresent invention overcomes the problems of the prior art by revolvingan arc to generate an arc wall. The are wall defines a volume filledwith vaporized material. Still further, the arc wall has thecharacteristic of passing a gas or vapor but is impervious to thepassage of solid particles or liquid droplets which are incident uponthe wall, provided that they do not strike the wall with too high aforce.

The are wall is created by causing a high current d.c. electric arc torevolve about an axis thereby describing a surface of revolution whichis the arc wall. The are extends between appropriate electrodes and isrevolved in a conventional manner such as by reason of the force (I X 8)developed when the arc current i interacts with a steady state magneticfield B. The are revolves at a rate such that insofar as the liquid orsolid material is concerned, it is omnipresent. On the other hand, gasor vapor, because of its relatively low viscosity, can flow through thearc wall; that is, it passes through points where the arc instanteouslyis not preent. Thus, in contradistinctlon to the liquid or solidmaterial, the gas or vapors see the are well as being porous.

Such an arc wall enables the heater to meet the oblectlves of keepingthe solid or liquid material to be heated in close proximity to theplasma for sufficient residence time to effect the necesary transfer ofenergy and to force the material to be heated into the hottest plasmavolume where the gas is dissociated in order to transfer the heat ofreassociation to the material to vaporize it. This is accomplishedbecause the arc wall is generally impervious to solid particles orliquid droplets impinging upon it. The revolving arc can be thought ofas a solid rod rotating at a very high rate. Any particle of materialincident upon the wall will have transferred to it a certain amount ofmomentum by reason of the impact from the revolving rod. The

particle might be stopped or, more likely, it is deflected. However,before the carrier gas in which the particle is immersed, which gas isflowing through the wall, can give the particle appreciable accelerationin a direction which would force it through the wall, it will be againstruck by the revolving are making its next revolution. When theparticle, upon its first impact with the arc wall is deflected, ittravels until it hits the arc wall at another point. It may be deflectedseveral times before it has sufficient residence time to vaporized. Thevaporization can develop any needed pressure above the wall. Moreover,each time the particle is impacted by the revolving arc (i.e., isincident upon the arc wall), it is in the hottest plasma volume wherethe gas is dissociated and the heat of reassociation can be transferredto the particle. Thus, sufficient residence time is achieved.

It therefore is an object of the present invention to provide a methodand apparatus for heating solid and liquid particulate material tovaporization or higher temperature using a revolving arc to generate anarc wall.

it is another object of the present invention to provide a method andapparatus for heating solid and liquid particulate material tovaporization or higher temperature using an arc wall to providesufficient residence time.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there are shown -in thedrawings forms which are presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

FIG. 1 is a sectional view of an apparatus for performing the invention.

FIG. 2 is a sectional view of another form of the invention whereinseparation of constituent species takes place.

FIG. 3 is a sectional view of yet another form of the invention forseparating constituent species of the material.

FIG. 4 is a sectional view of still another form of the invention forseparating constituent species of the material.

Referring now to the drawings in detail, wherein like numerals indicatelike elements, there is shown in FIG. 1 apparatus for heating solid orliquid particulate material to vaporize the same. As shown, the heatingapparatus 10 includes a chamber 12 into which is fed a carrier gas underpressure through inlet 14. The type and purpose of the carrier gas isdescribed below.

Within the chamber 12 is an annular electrode 16 and an axial electrode18. The annular outer electrode 16 may be connected to the positiveterminal of a high current source of direct current and the innercylindrical post electrode may be connected to the negative terminal ofthe same source. Both electrodes may be cooled by conventional means(not shown). The source of direct current is not shown since it isconventional. lt should be noted, however, that the polarity of theelectrodes can be reversed. The effect of such reversal will be toreverse the direction in which the are 20 revolves, assuming thedirection of the magnetic field B remains the same.

A solid cone 21 of a refractory material is fixed to the top of postelectrode 18. The purpose of the cone 21 is to prevent material beingheated from accumulating on the relatively cool post electrode 18. Thecone 21 is either electrically insulating or semi-insulating and iscooled only by heat transmission to the water cooled post electrode 18.It is sufficiently hot to prevent the material from condensing upon it.

The magnetic field B is generated by the magnetic coil 22 connected toan appropriate source of direct current. if desired, the magnetic coil22 can include a low temperature superconductor coil if a stronger fieldand hence higher angular velocities of the are 20 are desired. Morevoer,the magnetic field 8 need not be linear across the length of the arc.Indeed, a non-linear magnetic field can be used to shape the arc to astraight line as it revolves about its electrodes. However, it should bepointed out that in general the magnetic field B is parallel to the axisabout which the are 20 is to revolve and exists throughout the entireinterior of the chamber 12.

The structural walls of the chamber 12 are preferably electrically andthermally insulating. Appropriate cooling means (not shown) areprovided. Since such cooling means do not form a part of the presentinvention, they need not be described. The chamber 12 also includes agas outlet 24 through which the carrier gas and the vaporized materialis to flow. The gas outlet 24 may be connected to an appropriateseparator for separating the vaporized material from the carrier gas ifsuch separation is required. Such separator may not be necessary if thecarrier gas is also the vaporized material.

The material 26 is contained within a material chamber 28 having anappropriate feed apparatus 30 controlling the opening to a materialinlet 32 in the chamber 12. The feed apparatus 30 may be anyconventional means for injecting material in particulate form into thechamber 12 through the material inlet 32, such as a grooved roller asillustrated. Feed apparatus 30 is driven by a motor (not shown)connected to a pulley 34 fixed on shaft 36. The motor and pulley 34 areinterconnected by an appropriate belt.

The interaction of the magnetic field B and the current I flowingthrough the arc 20 extending between the electrodes 16 and 18, generatesa force (B X l) which causes the arc to revolve as indicated by showingthe are 20 in the phantom position. Thus, it may be said that themovement of the arc 20 causes it to describe a surface of revolution.This surface of revolution may be described as an arc wall and, in theexample shown, is a generally conical surface. Stated otherwise, the arcwall is effectively a coneshaped wall of highly heated gas and vaporhaving a temperature in the range of 4000K to 12,000K. The are normallypasses through the carrier gas which enters through inlet 14 and exitsthrough outlet 24. The carrier gas may, by way of example, be one of thenoble gases such as argon. Of course, other gases may be used asdesired. The carrier gas may be needed only for start-ups. Thereafter,only the vapors from the material 26 may be used.

The are 20 is typically about 2 to 4 mm. in diameter and carriesapproximately to 10,000 amperes. The arc would typically beapproximately 3 mm. in diameter. Accordingly, the thickness of the arcwall is 2 to 4 mm. with a typical wall thickness of 3 mm.

In order for the apparatus and process to work effectively, the arc mustrevolve at a high number of revolutions per minute. Accordingly, themagnetic field B is adjusted in respect to the current flowing throughthe are so that it revolves at a rate between 5000 to 100,000revolutions per minute. An optimum range for vaporizing small sizeparticles may be 12,000 revolutions per minute. At such a rate, therevolving are 20 passes through each point in the arc wall 200 times persecond. This makes it, for the purposes of this invention, onmipresentto the particulate material 26. At rates below 5000 rpm, theeffectiveness of the arc wall becomes lost. At rates above 100,000revolutions per minute, the are effectively may become a solid disc ofplasma. Thus, for uniform heating of material, the time for onerevolution of the are 20 must be considerably less than the timerequired for the material to pass (in the axial direction) through theregion being heated by the are.

An electric arc may be looked upon as having a core that is imperviousto the flow of gas or solid material through it. While this view may notbe absolutely correct, it is generally believed to be more correct thanassuming that the arc permits uniform flow through its thickness withonly moderate opposition. The temperature through an arc is a gradient.The core has a temperature of between approximately 10,000 to l4,000Ksurrounded by an enevelope at a lower temperature but greater than5000K. Beyond the envelope, the temperature drops off rapidly and isrelatively cool. Just the same, an electric are 20 can be viewed as ahot solid rod revolving at a fixed rate. The result is uniform andclosely controlled heating of material which comes in contact with orflows through the arc wall.

Gas, or vapor, because of its relatively low viscosity can flow throughthe arc wall, passing through points where the arc instanteously is notpresent. To the gas or vapor, the arc wall is porous. However, the arcwall is impervious to solid particles or liquid droplets impinging uponit. Thus, the material 26 should be particulate material or, ifinitially in a liquid form, it may be droplets.

As the particulate material 26 enters the chamber 12, it becomesimmersed in the carrier gas or material moving at a sufficiently lowvelocity and pressure to have little effect upon the particulatematerial 26, yet it should cause the material 26 once vaporized to flowthrough the arc wall and through outlet 24. The particulate materialfalls, generally under the force of gravity, until it strikes the arcwall. If gravity is not used, then another means to force theparticulate material 26 against the arc wall can be used. For example, acarrier gas or a material vapor at a somewhat higher pressure such thatit would entrain the particulate material or some means of projectingthe material into the chamber with an initial velocity can be used.

In any case, each particle, when incident upon the arc wall, whether itbe a drop of liquid or a solid particle, receives a certain amount ofmomentum by reason of the impact from the rotating electric are 20 whichlooks very much like a solid rod. The particle will be either stopped ordeflected to another point of incidence upon the arc wall. But beforethe gas or material vapor in which it is immersed can give the particleappreciable acceleration in a direction that would send it through thewall, it will be again struck by the rotating arc making its nextrevolution. The particle is once again deflected until it is incidentupon the arc wall at another point. It may be deflected many timesbefore it has sufficient residence time to be vaporized. But, itcontinues to make contact with the arc wall until it is vaporized andthus the requisite sufficient residence time is achieved. Thevaporization pressure is allowed to rise to an amount sufficient toforce the vapor and gases through the arc wall.

The residence time of liquid droplets and/or solid particles in thevicinity of the rotating arc is much increased by the following factors:(I) transfer of mo mentum from the rotating are 20; (2) differentialvaporization; (3) turbulence; and (4) entrainment in the circulatinggases and vapors. Transfer of momentum from the rotating arc has alreadybeen described.

The concept of differential vaporization may be de scribed as follows.At a certain elevation above the arc 20, such as at the material inlet32, a solid particle is released. The particles move downward under theinfluence of gravity and drag exerted by the environmental gasesincluding material vapor. and/or carrier gas, if used. When the particleis in contact with the plasma are 20, heat is being transferred from thehot plasma to the particle through the front face of the particle. Ifthe heat transfer rate is fast enough, and downward motion of theparticle is slow enough, the particle is melted and partially vaporized.In this case, vapor would be released from the front face of theparticle. This vapor ejection exerts a thrust on the particle, which hasa component in the upward or reverse direction in which it initiallymoved into contact with the are 20. Thus, the motion of the particle isgoverned by the gravitational force, drag forces, the thrust due tovapor ejection, and also to the momentum imparted to it by the solidcharacter of the rotating are 20.

If the heat transfer rate is so slow and the motion of the particle isso fast that there is no vapor released from the particle before it isfully immersed in the plasma are 20, the motion of the particle willagain be governed by the gravitational force and the drag forces. Theselatter forces tend to again direct the particle into the plasma are 20until is melted and vaporized. The net result then is the conversion ofthe solid particles into a vapor.

The combined effect of the transfer of momentum from the rotating are 20and the reverse thrust created by vapor ejection is so great that theparticle is trapped above the rotating plasma are 20 until on repeatedencounters it is completely vaporized.

It should be understood, however, that the use of vapor ejection tomaintain the particle within zone I is not absolutely necessary to theoperation of the heater 10. The transfer of momentum from the rotatingare 20 should be sufficient to accomplish this purpose, but it may beaided by the use of vapor ejection as described immediately above.

Thus, the apparatus 10 provides a solution to the problem of vaporizingmaterial by heat, that is, total enthalpy. As stated above, the problemof vaporizing material, particularly refractory material using theplasma of electrical discharges, is largely one of (l) keeping thematerial to be heated in close proximity to the plasma for a residencetime sufficiently long to effect the necessary transfer of energy, and(2) to force mate rial to be heated into the hottest plasma volume whenthe gas is dissociated in order to transfer the heat of re associationto material to vaporize and dissociate it The are wall enables bothobjectives to be met. It func tions to keep all solid and liquidmaterials in the zone which is generally defined by imaginary line 38and th! arc wall generated by the rotating arc 20. Only whei thematerial (such as Al,O is vaporized can it leavt zone I.

The rotating are also imparts high rotational velocities to the gasesand/or vapors in the volume defined as zone I. Any mass rotating withthe vapors will have a significant centrifugal force acting upon it. Theforce acting upon any mass within the zone I will be:

F mvlr where:

m is the mass r is the radius measured from the central axis of thevolume defined in zone I v is the velocity normal to the radius.

The force acting upon the mass can also be written as follows:

F (2r) mrrp' where:

d) is the rotation per second of the gas (and/or vapor) in the arc wallvolume. The gas and/or vapor within the zone I may consist of vaporizedmaterial and/or the carrier gas.

The particles of material 26 must necessarily become entrained in thewhirling gases and/or vapors. Thus, a centrifugal force is also appliedto them. Stated otherwise, the rotating arc acts like a solid stirringrod to cause the mass of gas and/or vapor to attain a high rotationalvelocity which tends to entrain material that enters arc wall volumedefined as zone I.

The net force exterted on a mass of gas or vapor at a particular radiusat the arc'wall is the difference between the force of restraint imposedby the wall and the centrifugal force on the mass at that point, withproper attention being given to the vector directions of the forces. Fora fixed magnetic field intensity B, current I, and rotational velocitysuch difference force is clearly dependent upon the radius r. Therefore,the arc wall created by the rotating are 20 is differentially permeablein that the net restraint imposed by the wall is a decreasing functionof the radius. This fact permits the arc wall to selectively pass thevapor particles of different mass as described below.

It is obvious that the angle of the are 20 with respect to the axis ofrotation has a direct effect upon the process. Such angle affects thecentrifugal forces of the rotating mass of gas and/or vapors and alsothe angle has an effect in creating an elevated temperature in zone Iwhich contributes to the heating of the solid and liquid material. Theangle of the rotating arc 20 must be chosen so as to avoid throwing thematerial 26 out of the zone I. The angle measured from the horizontal ofthe are 20 should be between and 60 with preferred range being betweenl5 and 45. If the angle becomes too great, then the arc follows themagnetic field too well and is therefore difficult to control.

Another factor which works together with the entrainment effect to keepthe particles in the arc volume (zone I) is the higher viscosities ofthe gas within the arc volume. Viscosity of the gas and/or vapor isproportional to the square root of temperature. Because of its extremelyhigh temperature, the viscosity of the gas and/or vapor within the arcwall volume is much higher than the adjacent cooler gases and/or vaporsbelow and above the arc wall volume.

The present invention is intended to be particularly useful invaporizing materials which have very high vaporization temperatures,such as A1 0 Within the arc volume defined by zone I, the temperature iswell in excess of the 3253K boiling point of M 0 lmportantly, thesevaporization temperatures exist only in the relatively small arc wallvolume defined as zone I. The temperatures above zone I and below theare 20 can be and are substantially less than 3000K. The walls of thehousing 12 therefore have still lower temperatures. Thus, difficultproblems of wall structure and cooling at temperatures in excess of3000K are avoided. Relatively simple solid walls made of commonmaterials can be used.

The present invention has been used to vaporize M 0 in the followingmanner. An apparatus similar to what is shown in FIG. 1 was constructedexcept no outlet 24 was provided. Thus, the vaporized material wasretained within the chamber 12. The water cooled copper electrodes 16and 18 were connected to a source of electrical power which developed 36kva. Argon was used as a carrier gas and injected through an inlet l4 at12 cubic feet per minute. The distance between the electrodes 16 and 18was 4 centimeters and an arc of that length was struck between theelectrodes with a resulting arc current of 400 amperes producing an arcvoltage of volts. The electrodes 16 and 18 are positioned such that theare 20 and hence the arc wall measured at an angle of 30 from thehorizontal. The magnetic coil 22 was energized by an appropriate sourceof electrical power so as to generate an axial magnetic field B equal to4000 gauss. As stated above, the material 26 was M 0 The charge wasparticles of chemically pure number 8 to number 14 mesh (0.060 0.080inch) particles which were fed downwardly onto the arc wall over aperiod of about 3 seconds. The arc duration after start of the particleinsertion was approximately 8 seconds. Following shut-down, examinationrevealed more than 80% of the particles of M 0 were vaporized. Stillfurther, a deposit of aluminum was found on the initially bright copperannular electrode 16. The reasons for this is discussed in respect tothe embodiments illustrated in FIGS. 3-4.

It has heretofore been explained that the arc wall developed byrevolving arc 20 is differentially permeable and that the net restraintis a decreasing function of radius (r) as measured from the central axisof the apparatus 10. This fact permits the arc wall to be used to pass,selectively, vapors of different mass. In other words, the arc wall canbe used as a separator.

Referring now to FIG. 2, there is shown an apparatus 10' similar to theapparatus 10 of FIG. 1 except that it has been modified to function as aseparator as well as a heater and vaporizer. Because of the similaritybetween the apparatus I0 and the apparatus 10', like elementsillustrated in FIG. 2 have been identified by primed numbers.Accordingly, a complete description of the apparatus illustrated in FIG.2 is not necessary. Rather, reference to the description of theapparatus in FIG. 1 can provide sufficient details as to the function ofvarious elements of the apparatus 10. Instead, what follows is adescription of those elements which differentiate the apparatus of FIG.2 from that of FIG. 1.

It may be that the material to be vaporized in the apparatus 10 consistsof a molecule made up of two atoms. For example, such material may be A10 Assume further that the magnetic field, current and rotational speedof the are 20' have been optimized for the vaporization of M 0 Ifvaporization takes place at a sufficiently high temperature, it will beaccompanied by dissociation into the components Al and O, with differentatomic masses of 27 and 16, respectively. Other materials may similarlydissociate into their atomic constituents or a mixture of two or moregases of any kind.

As previously stated, the arc wall generated by revolving arc 20'presents a uniform restraint to the gases and vapors whirling within thearc volume of zone I. However, a differential force due to the varyingcentrifugal forces is acting upon the arc wall. Since aluminum andoxygen have different atomic masses, the aluminum will pass through thewall at some radius r and the oxygen will pass through the wall at someradius r,. The radius r, must be smaller than the radius r, where theoxygen will feel sufficient centrifugal force to escape through the arcwall. The volume into which the oxygen escapes can be divided from thevolume into which the aluminum escapes by a dividing wall 40'. Wall 40'can be made of any material that is capable of withstanding hightemperatures, such as carbon. The aluminum can be condensed andcollected as a liquid on a cool wall surface of the chamber 12'. Theoxygen can be allowed to escape through the outlet 42' or in any otherconventional manner.

Thus, the apparatus [0' acts to separate constituent elements by heatingthem beyond vaporization to the point where they are dissociated.

As an alternative, the rotational speed 4; of the are 20' can be reducedto where the oxygen is not forced through the arc wall. Instead, thealuminum passes through the arc wall at some radius r, which is greaterthan r The oxygen can then be taken off from the arc volume (zone I) inany convenient manner such as through an opening provided in theelectrode 18'.

Regardless of whether the apparatus illustrated in FlGS. l and 2 is usedas a separator or not, it is apparent that the aluminum or heaviermolecules and of course the heavy particles prior to vaporization tendtoward the apex of the conical arc volume. This is advantageous sincethis is the hottest part of the arc volume. For this reason, it isadvantageous to arrange the feed apparatus 30 so that the particles ofmaterial 26 enter the arc volume defined by zone I relatively close tothe central axis.

Although the present invention has been illustrated as including onlyone revolving are 20 or 20, it should be understood that two or morerevolving arcs could be used. Thus, revolving arcs below the are 20could be provided so that additional heating of the vaporized materialtakes place. In this way, it may be possible to heat the vapor beyonddissociation even into partial or complete ionization.

Still further, it may be desirable to assist the heating effect of therevolving are by providing a plasma torch or other heating devices. Suchplasma torch may be located on the central axis of the device such as inthe position of the electrode 18. Of course, electrode 18' would have tobe modified so as to be annular and surround the torch.

In the embodiment illustrated in FIG. 1, it was assumed that theapparatus would take advantage of the semi-permeable nature of the arcwall and that the vaporized material would be exhausted through theoutlet 24. In the embodiment illustrated in F IG. 2 wherein theapparatus is used as a separator, the aluminum vapors are passed throughthe arc wall but the oxygen vapors, as pointed out, can be otherwiseexhausted, such as through an opening provided in the electrode 18'. Itshould therefore be pointed out that it is not necessary to causevaporized material to pass through the arc wall even where the processis used merely to vaporize, but not separate material. The rotating are20 provides an arc wall which in turn defines a volume (zone I) theinterior of which is filled with vaporized material. This is whatprovides the sufficiently long residence time to vaporize a solid orliquid particulate material. However, the vapor, once generated, can becaused to pass through the arc wall, or to rise upwards and away fromthe arc volume (zone I).

The vapor generated within the arc volume is caused to pass through thearc wall if the volume above the imaginary line 38 is a closed volume sothat the vaporization of the material causes a pressure build-up, or thepressure due to the carrier gas is sufficient, or the combination ofthese pressures is sufficient to force the vapors through the arc wall.

However, it is equally possible to vent the volume above the imaginaryline 38 through an opening provided in the walls of chamber 12. Byappropriate venting, there will be either no appreciable pressurebuildup or a small pressure build-up that is not sufficient to force thevapors through the arc wall. A small pressure build-up is preferredsince the back pressure can be used to force vapors through the vent.

Referring now to FIG. 3, there is shown a modification to the embodimentillustrated in FIG. 1 wherein an appropriate venting means 40" has beenprovided in the wall of chamber 12 above zone I. The apparatusillustrated in FIG. 3 is the same as the apparatus 10 in FIG. 1 exceptthat it has been modified as just described and in addition, the outlet24 has been eliminated. The apparatus illustrated in FIG. 3 isdesignated as apparatus 10" and like elements have been identified bydouble-primed numbers. Accordingly, a complete description of theapparatus illustrated in FIG. 3 need not be repeated herein.

A further modification of the embodiment illustrated in FIG. 3 is thedisplacement of inlet 14" to a position remote from the axis of theapparatus 10' so that the electrode 42" can be suspended co-axial withand above the post electrode 18". As shown, the electrode 42" isconnected to the electrode 16" by the resistor 46". This resistorprevents the are 20" from being transferred to the electrode 42" bymaintaining an appropriate potential difference.

The purpose of the apparatus 10" illustrated in FIG 3 can now beexplained. As indicated when describing an example of how M 0 can bevaporized, a coating or aluminum was found on the initially brightcopper electrode 16. Such a deposit of aluminum indicates tha separationof constituent parts of the material being va porized can be achieved.In the example given, alumi num was obviously separated from oxygenwhich is thr only other constituent part of A1 0,. The mechanisn bywhich the aluminum was separated from the oxygei is not completelyunderstood, but there are two mecha nisms by which such separation mayoccur. They an explained hereinafter. An important point, however, ithat aluminum separation was accomplished withou passing the vaporthrough the arc wall. The apparatu illustrated in FIG. 3 may be used toaccomplish sucl separation.

As stated, there are two possible processes or mecha nisms by which theapparatus illustrated in FIG. 3 ma be used to separate one constituentspecies of materit from the remaining constituent species. One process iby rapid quenching. Thus, in the example given, alum num may have beenquenched on the electrode 1t Rapid quenching is a recognized mechanismand is de scribed by Rains and Kadlec in Metallurgical Transac tions,Volume 1, pp. 1501-1506, published June, 197( 1 1 Rapid quenching canoccur if the work material is only dissociated.

The second process or mechanism by which separation can occur (e.g.,aluminum from oxygen) is when the material is both dissociated andpartly ionized. Where Al O is vaporized, the aluminum, having a lowerionization potential, is partly ionized. As such, it will beelectrically attracted to the electrode 16. It should also be noted thatboth the quenching and the ionization process may occur simultaneously.

From the foregoing, it can be seen that the apparatus illustrated inFIG. 1 can also be used to effect a separation process. Thus, if theelectrode 16 be a cathode and the vapors within zone I be heated untilat least partial ionization of the constituent species, such asaluminum, takes place, then the electric field will attract the partlyionized species to the cathode electrode and the pressure developedwithin and above zone I will force the other constituent species, suchas oxygen, to flow through the arc wall.

The apparatus illustrated in FIG. 3 can be used to separate aconstituent species from the remaining species with or withoutionization. In this instance, one of the species can be quenched or, ifionized, attracted to the cathode electrode and hence deposited out. There maining species, such as oxygen, can be freely vented through thevent 40". I

The embodiment of the apparatus illustrated in FIG. 3 includes the thirdelectrode 42" which may be referred to as a cold finger collector. Theelectrode 42" is preferably made of aluminum and is water cooled. Thevalue of the resistor 46" is preferably quite high, (e.g., two megohms)and serves to maintain the electrode 42 at a potential difference withrespect to the electrode 16" so that the are 20" will notjump toelectrode 42". Being cooled, the purpose of the electrode 42" is toquench one of the constituent species (e.g., aluminum) aftervaporization in a process wherein there is no ionization, onlydissociation. Thus, the cold finger collector 42" serves merely tosupplement the electrode 16" by causing one constituent of a dissociatedmaterial, such as aluminum, to condense upon its surface thus beingcollected apart from the remaining constituent species.

Referring now to FIG. 4, there is shown yet another embodiment of theinvention wherein the apparatus 110 can be used to separate an ionizedvapor species from un-ionized vapor species and also to separate andcollect that species by quenching on a cooled electrode. The apparatus 1illustrated in FIG. 4 is similar to the apparatus 10 in FIG. 1 exceptthat it has been modified as hereinafter described. Because of thesimilarity, like elements illustrated in FIG. 4 have been designatedwith similar numbers except that they are listed in hundreds rather thantens to distinguish the two devices. Accordingly, a complete descriptionof the apparatus 110 is not necessary. Rather, reference to thedescription of the apparatus in FIG. 1 can provide sufficient detail asto the function of various structural elements.

The apparatus 110 includes several additional cold finger collectorelectrodes 143. ()nly one of the electrodes 143 is fully shown. Adescription of one electrode 143 is sufficient since all of theelectrodes are of the same construction.

As shown, electrode 143 is suspended from the top wall of the chamber112 by the mechanism 150 which includes conventional means such as ahydraulic ram for adjusting the height of the electrode 143 is relationto the electrodes I16 and 118. Electrode 143 is preferably made ofaluminum and is water cooled by conventional means so that it isnormally at a substantially lower temperature than the electorde 116.Electrode 143 is connected through resistor 146 to voltage supply 148.Voltage supply 148 is also connected to electrode 116. The purpose ofvoltage supply 148 is to maintain electrode 143 at a higher negativepotential than the electrode 116. Preferably, the electrode 143 is at ahigher negative potential of between 20 to volts with respect toelectrode 116. Resistor 146 is a limiting resistor having a value ofbetween 2 to 10 ohms. All of the electrodes 143 are spaced apart equallyand located at the same radial distance measured from the central axisof the apparatus 110.

The purpose of providing electrodes 143 is to collect ionized vaporsfrom within the zone I. Because of their higher negative potential,ionized vapors will now be drawn to the electrodes I43 rather than tothe cathodic electrode 1 16. The advantage of such electrodes is thatthey provide a separate collector location that is neither disturbed norstrongly heated by the rotating are 120.

The apparatus 150 raises each of the electrodes 143 so as to maintainthe position of their distal end approximately at the boundary of zone I(imaginary line 138). This provides for the formation of aluminum rodson a continuous basis.

There are three electric fields which exist simultaneously within theapparatus to affect the ions within the zone I. There is the electricfield extending between the electrodes 143 and the anode post electrode118. There is also an electric field between the electrodes 143 and thecathodic annular electrode 116. Still further, there is the electricfield between the electrodes 143 and the rotating are 120. This latterfield is strongest when the are is immediately below any particularelectrode 143. In the absence of positive ion flow to the electrode 143,such electrodes are negative by the full voltage of the voltage supply148. Once ion flow commences, the negative potential of any one of thecollectors 143 falls clue to the ion current flow through resistor 146until it approaches the voltage potential of electrode 116. However, itcannot fall as low as the potential of electrode 116 because under suchcircumstances current could not be attracted to the electrodes 143.Resistor 146 prevents transferring the are from electrode 116 to one ofthe electrodes 143 as does the resistor 46" in the apparatus in FIG. 3.

In the embodiment shown in FIG. 4, the uncollected gases, such as oxygenwhen A1 0; is vaporized, are exhausted through vent 140. In thealternative, vent may be closed and pressure allowed to build until theuncollected gases are driven through the arc wall and exhuasted throughoutlet 124. Outlet 124 would normally be closed when vent 140 is beingused.

If desired, either or both electrodes 118 and 116 can be made of carbonrather than copper. This may be advantageous when separating aluminumout of dissociated M 0 Thus, evaporated carbon atoms or ions can combinewith the O to form CO. In this way, contamination of the collectedaluminum by evaporated can be avoided.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to 13 the foregoing specification as indicating the scope of theinvention.

I claim:

l. A process for separating the constituent species of solid or liquidparticulate material by increasing the residence time of the material ina high temperature zone, comprising the steps of:

revolving an electric are extending between two electrodes to define asurface of revolution, said surface of revolution including within itsboundaries an arc volume;

directing said particulate material so as to be incident upon saidsurface of revolution; revolving said are at a rate sufficient to makethe surface of revolution impervious to particulate material in solid orliquid form and to heat the particulate material within the arc volumeso that at least a portion of the particulate material is vaporizedanddissociated into constituent species; and

removing at least one of the dissociated constituent species from thearc volume.

2. A process in accordance with claim 1 wherein the step of removing atleast one of the dissociated constituent species includes passing thedissociated constituent species through the surface of revolution.

3. A process in accordance with claim 1 wherein the step of removing atleast one of the dissociated constituent species includes venting thatspecies away from said are volume through a surface remote from saidsurface of revolution.

4. A process in accordance with claim 1 wherein the step of removing atleast one constituent species includes condensing the one constituentspecies upon a surface that is below the vaporization temperature ofthat species and at a lower temperature than the temperature within thearc volume.

5. A process in accordance with claim 4 wherein the step of condensingat least one constituent species includes condensing said species uponan electrode.

6. A process in accordance with claim 4 wherein the step of condensingthe one constituent species includes condensing said species upon athird electrode to which the arc current does not flow.

7. A process in accordance with claim 1 including revolving said are byinteracting it with a magnetic field.

8. A process in accordance with claim 1 wherein said constituent specieshave significantly different masses and said step of removing at leastone of the dissociated constituent species from the arc volume includes:

passing more than one dissociated constituent species through thesurface of revolution while maintaining the particulate material withinsaid are volume; and

separating at least one species from the other species passed throughsaid surface of revolution by passing said at least one species throughan area of the surface of revolution that is different from the areawhere said other species passed through said surface of revolution asdetermined by the different centrifugal forces applied to eachconstituent species depending upon its mass and rotational velocity; and

guiding that separated constituent species away from said are volume.

9. A process in accordance with claim 1 including entraining saidparticulate material within a mass of gas revolving within said arevolume.

10. A process in accordance with claim 9 wherein said mass of gasincludes said material in a gaseous form.

11. A process in accordance with claim I wherein said surface ofrevolution is generally conical.

12. A process in accordance with claim 11 including positioning saidconical surface of revolution at an angle to define an arc volume thatmaximizes the residence time for said particulate material.

13. A process in accordance with claim 11 wherein the angle of saidconical surface of revolution measured from a surface normal to the axisof said conical surface is 15 to 60.

14. A process in accordance with claim 1 including revolving said arc ata rate between 5000 to l00,000 revolutions per minute.

15. A process in accordance with claim I the steps of causing a mass ofgas to revolve within the arc volume and entraining said particulatematerial within said revolving mass of gas within said are volume.

16. A process in accordance with claim 15 wherein said revolving mass ofgas includes the dissociated constituent species of the vaporizedparticulate material.

17. A process for separating the constituent species of solid or liquidparticulate material by increasing the residence time of the material ina high temperature zone, comprising the steps of:

moving an electric are extending between electrodes to define an arcwall including within its boundaries an arc volume; directing saidparticulate material into said are volume so as to be incident upon saidare wall;

increasing the residence time of the particulate material inside saidarc volume sufficiently to permit the transfer of heat energy to saidparticulate material so that at least a portion of the particulatematerial is vaporized and dissociated into constituent species; and

removing at least one of the dissociated constituent species from thearc volume.

18. A process for vaporizing solid or liquid particulate material byincreasing the residence time of the material in a high temperaturezone, comprising the steps of:

revolving an electric are extending between two electrodes to define asurface of revolution, said surface of revolution including within itsboundaries an arc volume;

directing said particulate material so as to be incident upon saidsurface of revolution;

revolving said are at a rate sufficient to make the surface ofrevolution impervious to particulate material in solid or liquid formand to heat the particulate material within the arc volume so that atleast a portion of the particulate material is vaporized; and

removing said vaporized material from said are volume.

19. A process in accordance with claim 18 including removing saidmaterial in its gaseous form by passing the gaseous material throughsaid surface of revolution while maintaining said particulate materialwithin said are volume by means of said revolving arc.

20. A process in accordance with claim 18 including removing saidmaterial in its gaseous form by venting it away from said are volumethrough a surface remote from said surface of revolution.

21. A process in accordance with claim 18 wherein said surface ofrevolution is generally conical.

22. A process in accordance with claim 21 including positioning saidconical surface of revolution at an angle to define an arc volume thatmaximizes the residence time for said particulate material.

23. A process in accordance with claim 21 wherein the angle of saidconical surface of revolution measured from a surface normal to the axisof said conical surface is to 60.

24. A process in accordance with claim 18 including revolving said arcat a rate between 5,000 to 100,000 revolutions per minute.

25. A process in accordance with claim 18 including revolving said areby interacting it with a magnetic field.

26. A process for separating the constituent species of solid or liquidparticulate material by increasing the residence time of the material ina high temperature zone, comprising the steps of:

revolving an electric arc extending between two electrodes to define asurface of revolution, said surface ef revolution including within itsboundaries an arc volume; directing said particulate material so as tobe incident upon said surface of revolution; revolving said arc at arate sufficient to make the surface of revolution impervious toparticulate material in solid or liquid form and to heat the particulatematerial within the arc volume so that at least a portion of theparticulate material is vaporized and dissociated into constituentspecies and at least one of those species is at least partly ionized;and removing the partly ionized species from the arc volume byelectrically attracting that species to an electrode of oppositepolarity. 27. A process in accordance with claim 26 wherein the step ofelectrically attracting the species partly ionized includes attractingthat species to a third electrode to which the arc current does notflow.

I F I l'

1. A PROCESS FOR SEPARATING THE CONSTITUENT SPECIS OF SOLID OR LIQUIDPARTICULATE MATERIAL BY INCREASING THE RESIDENCE TIME OF THE MATERIAL INA HIGH TEMPERATURE ZONE, COMPRISING THE STEPS OF: REVOLVING AN ELECTRICARE EXTENDING BETWEEN TWO ELECTRODES TO DEFINE A SURFACE OF REVOLUTION,SAID SURFACE OF REVOLUTION INCLUDING WITHIN ITS BOUNDARIES AN ARCVOLUME; DIRECTING SAID PARTICULATE MATERIAL SO AS TO BE INCIDENT UPONSAID SURFACE OF REVOLUTION; REVOLVING SAID ARC AT A RATE SUFFICIENT TOMAKE THE SURFACE OF REVOLUTION IMPERVIOUS TO PARTICULATE MATERIAL INSOLID OR LIQUID FORM AND TO HEAT THE PARTICULATE MATERIAL WITHIN THE ARCVOLUME SO THAT AT LEAST A PORTION OF THE PARTICULATE MATERIAL ISVAPORIZED AND DISSOCIATED INTO CONSTITUENT SPECIS; AND REMOVING AT LEASTONE OF THE DISSOCIATED CONSTITUENT SPECIES FROM THE ARC VOLUME.
 2. Aprocess in accordance with claim 1 wherein the step of removing at leastone of the dissociated constituent species includes passing thedissociated constituent species through the surface of revolution.
 3. Aprocess in accordance with claim 1 wherein the step of removing at leastone of the dissociated constituent species includes venting that speciesaway from said arc volume through a surface remote from said surface ofrevolution.
 4. A process in accordance with claim 1 wherein the step ofremoving at least one constituent species includes condensing the oneconstituent species upon a surface that is below the vaporizationtemperature of that species and at a lower temperature than thetemperature within the arc volume.
 5. A process in accordance with claim4 wherein the step of condensing at least one constituent speciesincludes condensing said species upon an electrode.
 6. A process inaccordance with claim 4 wherein the step of condensing the oneconstituent species includes condensing said species upon a thirdelectrode to which the arc current does not flow.
 7. A process inaccordance with claim 1 including revolving said arc by interacting itwith a magnetic field.
 8. A process in accordance with claim 1 whereinsaid constituent species have significantly different masses and saidstep of removing at least one of the dissociated constituent speciesfrom the arc volume includes: passing more than one dissociatedconstituent species through the surface of revolution while maintainingthe particulate material within said are volume; and separating at leastone species from the other species passed through said surface ofrevolution by passing said at least one species through an area of thesurface of revolution that is different from the area where said otherspecies passed through said surface of revolution as determined by thedifferent centrifugal forces applied to each constituent speciesdepending upon its mass and rotational velocity; and guiding thatseparated constituent species away from said arc volume.
 9. A process inaccordance with claim 1 including entraining said particulate materialwithin a mass of gas revolving within said arc volume.
 10. A process inaccordance with claim 9 wherein said mass of gas includes said materialin a gaseous form.
 11. A process in accordance with claiM 1 wherein saidsurface of revolution is generally conical.
 12. A process in accordancewith claim 11 including positioning said conical surface of revolutionat an angle to define an arc volume that maximizes the residence timefor said particulate material.
 13. A process in accordance with claim 11wherein the angle of said conical surface of revolution measured from asurface normal to the axis of said conical surface is 15* to 60* .
 14. Aprocess in accordance with claim 1 including revolving said arc at arate between 5000 to 100,000 revolutions per minute.
 15. A process inaccordance with claim 1 the steps of causing a mass of gas to revolvewithin the arc volume and entraining said particulate material withinsaid revolving mass of gas within said arc volume.
 16. A process inaccordance with claim 15 wherein said revolving mass of gas includes thedissociated constituent species of the vaporized particulate material.17. A process for separating the constituent species of solid or liquidparticulate material by increasing the residence time of the material ina high temperature zone, comprising the steps of: moving an electric arcextending between electrodes to define an arc wall including within itsboundaries an arc volume; directing said particulate material into saidarc volume so as to be incident upon said arc wall; increasing theresidence time of the particulate material inside said arc volumesufficiently to permit the transfer of heat energy to said particulatematerial so that at least a portion of the particulate material isvaporized and dissociated into constituent species; and removing atleast one of the dissociated constituent species from the arc volume.18. A process for vaporizing solid or liquid particulate material byincreasing the residence time of the material in a high temperaturezone, comprising the steps of: revolving an electric arc extendingbetween two electrodes to define a surface of revolution, said surfaceof revolution including within its boundaries an arc volume; directingsaid particulate material so as to be incident upon said surface ofrevolution; revolving said arc at a rate sufficient to make the surfaceof revolution impervious to particulate material in solid or liquid formand to heat the particulate material within the arc volume so that atleast a portion of the particulate material is vaporized; and removingsaid vaporized material from said arc volume.
 19. A process inaccordance with claim 18 including removing said material in its gaseousform by passing the gaseous material through said surface of revolutionwhile maintaining said particulate material within said arc volume bymeans of said revolving arc.
 20. A process in accordance with claim 18including removing said material in its gaseous form by venting it awayfrom said arc volume through a surface remote from said surface ofrevolution.
 21. A process in accordance with claim 18 wherein saidsurface of revolution is generally conical.
 22. A process in accordancewith claim 21 including positioning said conical surface of revolutionat an angle to define an arc volume that maximizes the residence timefor said particulate material.
 23. A process in accordance with claim 21wherein the angle of said conical surface of revolution measured from asurface normal to the axis of said conical surface is 15* to 60* .
 24. Aprocess in accordance with claim 18 including revolving said arc at arate between 5,000 to 100,000 revolutions per minute.
 25. A process inaccordance with claim 18 including revolving said arc by interacting itwith a magnetic field.
 26. A process for separating the constituentspecies of solid or liquid particulate material by increasing theresidence time of the material in a high temperature zone, comprisingthe steps of: revolving an electric arc extending between two electrodesto define a surFace of revolution, said surface of revolution includingwithin its boundaries an arc volume; directing said particulate materialso as to be incident upon said surface of revolution; revolving said arcat a rate sufficient to make the surface of revolution impervious toparticulate material in solid or liquid form and to heat the particulatematerial within the arc volume so that at least a portion of theparticulate material is vaporized and dissociated into constituentspecies and at least one of those species is at least partly ionized;and removing the partly ionized species from the arc volume byelectrically attracting that species to an electrode of oppositepolarity.
 27. A process in accordance with claim 26 wherein the step ofelectrically attracting the species partly ionized includes attractingthat species to a third electrode to which the arc current does notflow.